Pasteurized eggs are relatively new items of commerce in the United States, and indeed, throughout the world. While the art has sought for sometime to devise effective methods for pasteurizing eggs, as described in detail in U.S. Pat. No. 5,843,505, which patent is incorporated herein by reference and relied upon for disclosure, until the existence of the process described and claimed in that patent, pasteurizing of eggs had not been successful either from a commercial point of view or a functionality point of view. Functionality refers to a group of properties of eggs including yoke index, Haugh units, yoke strength, angel cake volume, sponge cake volume, foam stability, whippability, and lysozyme properties. All of these functionalities are well known to the art and are described in detail in the above-noted patent and, for conciseness herein will not be described in detail. However, for example, the angel cake volume is sensitive to egg white protein damage. Heat damage to the protein will increase whipping time and decrease cake volume. Foam stability is a measure of the volume of foam of whipped egg whites. Heat damaged white protein will provide less foam volume and therefore is less desirable in making meringues and the like. Haugh units also measure the foam stability of whipped egg whites and is important in many uses of eggs for baking and cooking. Yoke index is a measure of the yoke height versus the yoke width. When breaking a fresh egg into a pan for frying, if the yoke index is not proper, the yoke will look flat and unappealing in a sunny side up fried egg. Yoke strength is a measure of the strength of the yoke membrane to retain the yoke and is important when frying eggs.
The above-noted U.S. Patent describes and claims processes where eggs may be pasteurized in keeping with the relatively new U.S. Food and Drug Administration definition of pasteurized eggs, which includes a requirement that any Salmonella species in the egg is reduced by an amount equal to at least 5 logs. Those processes are also carried out such that the pasteurized eggs do not have substantial loss of functionality, particularly in regard to the Haugh units, as well as the yoke index and yoke strength.
As a result of the processes described and claimed in that patent, substantial commercialization of pasteurized eggs has now taken place.
Very basically, the processes entail heating raw eggs in a heat transfer medium at certain temperatures within certain parameter lines of a graft shown in that patent and for a time sufficient that a Salmonella species which may be present in the eggs is reduced by an amount of at least 5 logs. In one example of that patent, the internal temperature of the yoke is brought to 133xc2x0 F. and maintained at that temperature by addition of heated or cooled water to a pasteurizer until any Salmonella bacteria in the egg is reduced by at least 5 logs. Depending upon the particular pasteurizer, the history of the raw eggs being pasteurized, the temperature of the raw eggs entering the pasteurizer and their size, ambient temperatures around the pasteurizer, as well as other factors, a total pasteurizing time of somewhere about 64 minutes or more is required. Of course, the time of dwell of the central portion of the yoke of the eggs being pasteurized will be considerably less than that in accordance with the parameter lines A and B of the graft in that patent. However, the 64 minutes so called total processing time, including the time required to bring the yokes to the temperatures required by that patent for pasteurization, substantially increases the cost of production of pasteurized eggs. It would, of course, be of a substantial advantage to the art to considerably shorten the total processing time required for such pasteurization.
Also, it was found that eggs, which are commercially pasteurized according to that patent, do not have the extended shelf life of the eggs pasteurized in the examples of that patent. Indeed, in commercial pasteurization of the eggs, it was found that a substantial percentage of the pasteurized eggs, even with proper traditional storage conditions, unexpectedly had a shelf life of only about 21 days before rot began to appear in the pasteurized eggs. This, of course, was of concern in regard to the commercial operation, and it was well recognized that this is a disadvantage in the commercial process of pasteurizing eggs and that it would be of substantial advantage to the art to considerably extend the shelf life of the commercially pasteurized eggs.
The above-noted patent also discloses that the heat transfer medium for pasteurizing the eggs may be heated to more than one temperature during the pasteurizing process. However, as a practical matter, having the heat transfer medium, e.g. water, at different temperatures, provides advantages and more efficiency, but requires a series of separate pasteurizing tanks, along with the added capital costs. This also requires placing large volumes of eggs in one tank, removing the eggs from that tank, and placing and removing the eggs from a succeeding tank or tanks. It was determined that using multiple tanks and the apparatus for moving the eggs in and out of the tanks not only complicated the pasteurizing process, but substantially increased the cost thereof. In this latter regard, one of the hazards of pasteurizing eggs is that if during handling eggs break in a pasteurizing tank, then for food safety reasons, the process must be stopped, the tank drained, well-cleaned, and replenished with hot water. It was therefore recognized that it would be a substantial advantage to carry out the pasteurizing process at multiple temperatures but without the necessity of using multiple tanks. This would provide the advantages disclosed in the aforementioned patent that multiple temperatures of pasteurization can decrease the total time required for pasteurization and, thus, substantially reduce the pasteurization costs.
Further, the prior art considered it important that the eggs be removed from the pasteurizer as soon as a 5 log reduction of any Salmonella in the eggs is achieved. This is in order to prevent unwanted additional pasteurization, i.e. above the 5 logs safety requirement, which would adversely affect the functionality of the pasteurized eggs. However, this rather rigid requirement in the pasteurization, as it was perceived by the art, made it difficult to precisely achieve that 5 log reduction, while at the same time retaining the functionality of fresh raw eggs, without very careful control of the pasteurization process, along with expensive and extensive control devices. It would, of course, be of an advantage to the art to pasteurize eggs without such expensive control.
In regard to the above-discussed advantage of reducing the total pasteurization time, it was discovered that the total pasteurization time could be reduced by certain uses of multi-temperatures in the pasteurization process. These certain multi-temperatures include at least three different temperatures or temperature ranges, and especially where a first temperature(s) encountered by the eggs is at a higher temperature(s), a second temperature(s) encountered by the eggs is at a preferred pasteurization temperature(s), and a third temperature(s) encountered by the eggs is again at a higher temperature(s). More precisely, the first temperature(s) should be between about 139xc2x0 F. and 146xc2x0 F., the second temperature(s) should be between about 130xc2x0 F. and less than 135xc2x0 F., and the third temperature(s) should be between about 135xc2x0 F. and 138xc2x0 F. As a subsidiary discovery in this regard, it was found that, however, the time in which the eggs dwelled at the three different temperatures or temperature ranges must be different with a shorter time at the first higher temperature(s), a longer time at the second more desired pasteurization temperature(s), and a shorter time at the higher third temperature(s).
As another discovery in this regard, it was found, contrary to the understanding in the art, that the eggs need not be pasteurized to at least a 5 logs reduction of Salmonella in the pasteurizer, e.g., a pasteurization water bath. Prior to the present invention, it was considered essential that the eggs reach a 5 logs reduction in the pasteurization water bath and after the 5 logs reduction, the eggs are immediately removed from the pasteurization bath and placed in a chilled water bath to prevent further heating, pasteurization, and deterioration of functionality that would be caused by further pasteurization. It has been found, contrary thereto, that the eggs can be removed from the pasteurization bath when reaching only about a 4.6 logs, e.g., a 4.8 logs reduction, especially about a 4.75 logs reduction, and that residual heat in the eggs will achieve the 5 logs reduction after the eggs are removed from the pasteurizer. When the eggs are immediately passed into a gaseous atmosphere, e.g., air, after removal from the pasteurizer, pasteurization will continue to occur until the eggs reach a temperature below about 128xc2x0 F. Thus, during that dwell in the gaseous atmosphere, additional pasteurization will take place and will reach at least a 5 log reduction.
As another important discovery, it was found that in a conventional elongated pasteurizing tank, even though the water therein is a single body of water, it is possible to generate different temperature zones along a major axis of that tank such that the temperatures noted above could be achieved. This is because heat generated in localized zones within the tank can form zones of different temperatures by way of vertical convection of the water in the tank.
As another discovery in this regard, it was found that the different temperature zones can be substantially sharpened into distinct temperature compartments having different temperatures by use of a plurality of series of transverse jets spaced apart along a major axis of the tank. These jets cause a jet fluid to pass from the bottom of the tank toward the top of the tank and provide something of a jet fluid wall for containment of the water at the different temperatures.
Also, it was found that after pasteurization of the eggs in the pasteurizer, and when the eggs are in the gaseous atmosphere, mentioned above, that the eggs should be contacted with an antibacterial fluid containing an antibacterial agent. Thus, any unwanted bacteria, such as rot bacteria and air borne pathogens, which might penetrate the eggs during cooling in the gaseous atmosphere, are substantially killed or very significantly reduced in number by the antibacterial agent in the antibacterial fluid, such that the eggs are will rot during long term refrigerated storage. In deed, this is applicable to protect from rot bacteria any at least partially pasteurized egg that is in a heated condition, that is applying to that egg an antibacterial fluid containing an antibactericide.
Thus, briefly stated, in one regard, the present invention provides a method of pasteurizing in-shell chicken eggs by placing the eggs in a heated fluid having a temperature between about 128xc2x0 F. and 146xc2x0 F. The eggs are allowed to dwell in the heated fluid until there is a log reduction of at least 4.6 of any Salmonella bacteria within the eggs. The eggs are removed from the heated fluid and placed in a gaseous atmosphere. Thereafter, the eggs are contacted with an antibacterial fluid containing an antibacterial agent, so as to prevent rot in the eggs, as briefly mentioned above and explained in more detail below.
More preferably, the eggs are placed in the heated fluid where the heated fluid has a first temperature(s) of about 139xc2x0 F. to 146xc2x0 F., a second temperature(s) from about 130xc2x0 F. to less than 135xc2x0 F., and a third temperature(s) from about 135xc2x0 F. to 138xc2x0 F. The first, second, and third temperatures of the heated fluid are maintained in separate zones of the heated fluid. The eggs are allowed to pass through the first, second, and third temperatures in a time period which causes a log reduction of at least 4.6 and preferably at least 4.75 of any Salmonella bacteria in the eggs. The eggs are removed from the heated fluid and passed into the gaseous atmosphere where the eggs are allowed to cool and further pasteurize so as to reach a log reduction of at least 5.0.
In a preferred form of the invention, the heated fluid is water and the water is contained in a tank, especially, an elongated tank through which the eggs traverse from an entrance end of the tank to a middle zone of the tank and to an exit end of the tank. Near the bottom of the tank a plurality of jets are disposed through which a jet fluid is passed. Some of the jets are arranged transverse to a major axis of the tank and are spaced apart such that the jet fluid rises vertically to at least near the top of the tank to provide a jet fluid wall near each of the spaced apart series of jets. This provides more sharply defined different temperatures along the major axis of the tank, particularly for increasing the speed and especially the precision of pasteurization and to reduce the loss of functionally.
In a further preferred form of the invention, not only is the antibacterial fluid contacted with the eggs after the eggs exit the pasteurizing tank, but the antibacterial fluid is contacted with mechanical equipment handling the eggs subsequent to the eggs exit of the pasteurizing tank. This avoids viable amounts of bacteria on any of the mechanical equipment from entering into the eggs.
In another form of the invention, after the eggs have been contacted, e.g. sprayed, with antibacterial fluid, the eggs are at least partially coated with a sealant to prevent entrance of bacteria into the eggs after processing.
In another form of the invention, the eggs are allowed to dwell in the heated fluid for a time sufficient to cause at least a 6 and up to 12 logs reduction of the Salmonella bacteria. This will produce a partially coagulated or cooked egg which is useful in the fast-food and nursing industries, since the egg is not only highly reduced in any possible Salmonella, but will cook much more quickly in preparing, for example, sunny side up eggs.